1. Field of the Invention
This invention relates to a constant voltage circuit formed of field effect transistors (FETs) such as metal-oxide-semiconductor (MOS) transistors and a reference voltage generating circuit to be used therefor.
2. Description of the Prior Art
As known previously, a conventional constant voltage circuit is of a bandgap reference circuit formed of bipolar transistors in general, and a practically usable constant voltage circuit formed entirely of MOS transistors is not known. Under such a circumstance, a constant voltage circuit capable of being realized on an MOS integrated circuit has been demanded to be developed in order to utilize various advantages of the MOS transistor.
The MOS transistor is large in production variation and has a non-linear temperature characteristic different from the bipolar transistor whose temperature variation is linear. As a result, in order to make a constant voltage circuit requiring good temperature characteristic of MOS transistors, it is an important problem how the temperature characteristic of such MOS transistors is controlled.